A difficulty encountered in the development of microwave or millimeter wave tubes has been the unavailability of a viable ruggedized high current density cathode capable of operating at current densities of 2A/cm.sup.2 to 30A/cm.sup.2 in the temperature range of 900 degrees C. to 1125 degrees C.
Heretofore, tungstate cathodes made by high compaction pressing have been used to meet high current density requirements. The difficulty with such cathodes has been their inability to be made in any geometry capable of operating at 2A/cm.sup.2 to 30A/cm.sup.2 in the temperature range of 900 degrees C. to 1125 degrees C. Moreover, the fabrication of the cathode is costly; the shape in which it can be mae is limited; the cathode is subject to degradation; and its emitter life is too short. Then too, cathodes fabricated by high compaction pressing require special handling.